YZ400 Head questions

fastcr500

On the YZ400f head on the left side, there is a hole. Is this supposed to be plugged with a soft plug or something? Is it an overflow hole? When I start my 400 I let it run and after running for a bit, coolant starts to come out after I shut it off. Not much but alittle. I just replaced the cylinder and am curious if this is normal due to to much coolant or if it is something I should take a look at. Thanks.

grayracer513

That is the drain for the spark plug well, which allows water, oil from a leaking cam cover, combustion gas from a loose plug, or whatever, to drain away, and also prevents a build up of air/gas pressure from popping the plug boot off.

Coolant should never come from this hole unless the head is cracked from the water jacket into the hole. How certain are you that it's coolant you see?

fastcr500

Positive. Its greenish fluid. My head is cracked in the water jacket, but I tried to fix it with JB weld. Apparently it is cracked inside the water jacket where I cant see. Looks like I need a new head.